Large power generators occasionally fail due to thermal degradation of various materials, particularly organic insulation. Since an early detection of the insulation failure is essential to the prevention of a large-scale burn-out of the generator, monitoring devices are used which monitor the gas stream that flows through the generator. Presently, most monitors work by detecting particulates in the gas stream, which are formed when insulation is being thermally degraded. When the monitor detects degradation products and generates a signal, the flow of detectable particulates to the monitor is manually terminated to determine whether the signal is genuine or is due to a malfunction in the monitor. If the signal then terminates it is assumed to be genuine and the generator is shut down and the repair is made.
Since down time on a large generator can cost over $100,000 a day it is important to locate the insulation failure and repair it quickly. Over 50 different meterials are used in generators including regular and modified epoxies, polyesters, silicones, phenolics, etc. and unless the failure is easily visible, it may be very difficult to locate.